1. Technical Field
The present invention relates generally to an improved data processing system and, in particular, to a method and apparatus for testing a communications link in a data processing system. Still more particularly, the present invention relates to a method and apparatus for testing a modem line connected to a data processing system.
2. Description of the Related Art
References to the internet and the "information superhighway" are becoming more pervasive on television and in newspapers. Advertisers are publishing http://www . . . addresses for all nature of commerce. The terms E-mail, electronic banking, and shopping from home are becoming familiar ideas to the average consumer.
As a result, a number of companies are developing systems for accessing the internet along with the World Wide Web. In particular, the network computer (NC), also called a web PC, java terminal, internet access device, browser box, etc., are computers that discard overweight operating systems and bloated platform specific applications. Typically, the systems will run microkernal operating systems and platform independent software. The systems are directed towards corporations as low cost work stations and to consumers as a lower cost, simple to use system in contrast to a typical personal computer for access to the internet. With respect to NCs being developed for consumers, these products are being offered as an appliance that provides a convergence between a television, videocassette recorder, telephone, answering machine, and a computer in a simple-to-use form. In many cases, all of these functions may be found within a single box.
The connectivity that people seek with respect to the internet and the "information superhighway" is provided by a modem, which allows the consumer's NC to establish a communications link with other data processing systems and exchange files, programs, images, and information across the telephone lines. Modems are a necessary bridge between the digital signals used in a computer and the analog signals used in a typical public switched telephone system. A function of the modem is to connect binary data signals from the NC into analog signals suitable for transmission over the PSTN. Additionally, the modem converts analog signals back into digital signals received from the PSTN from a remote data processing system.
Presently available modems allow an NC to determine whether a dial tone is present. Such an indication may be useful in the event that the modem is not connected to the telephone system. This indication of whether a dial tone is present, however, does not always accurately indicate whether the modem is connected to the telephone system. One example is the situation in which the NC has its modem connected to the same telephone line as another telephone. If the NC attempts to establish a communications link with another data processing system and another person is using that other telephone, an indication would be returned that no dial tone was present. This situation is distinguished from the situation in which the modem actually is not connected to the telephone line.
The typical consumer using an NC may be discouraged about such a situation and unable to discover why a dial tone is not present. As a result, the consumer is apt to return the appliance believing that the NC is defective. Therefore, it would be advantageous to have an improved method and apparatus for determining whether a modem is connected to a telephone line.